The 2nd International Conference on Biomedical Engineering and Biotechnology (iCBEB 2013), held i... more The 2nd International Conference on Biomedical Engineering and Biotechnology (iCBEB 2013), held in Wuhan on 11–13 October 2013, is an annual conference that aims at providing an opportunity for international and national researchers and practitioners to present the most recent advances and future challenges in the fields of Biomedical Information, Biomedical Engineering and Biotechnology. The papers published by this issue are selected from this conference, which witnesses the frontier in the field of Biomedical Engineering and Biotechnology, which particularly has helped improving the level of clinical diagnosis in medical work.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
h i g h l i g h t s • Three intercalation regions of the bentonite interlayers according to the s... more h i g h l i g h t s • Three intercalation regions of the bentonite interlayers according to the surfactant type. • Non-ionic surfactant inhibited intercalation and changed interlayer conformation. • Lecithin caused extensive bentonite intercalation and increased thermal stability.
A novel polymeric heart valve shows durability equivalent to 25 years in accelerated bench testin... more A novel polymeric heart valve shows durability equivalent to 25 years in accelerated bench testing, in vitro hydrodynamics equivalent to existing bioprosthetic valves; and good performance in a small acute feasibility study in sheep.
Circulation: Cardiovascular Quality and Outcomes, 2017
Background— In recent years, use of transcatheter aortic valve replacement has expanded to includ... more Background— In recent years, use of transcatheter aortic valve replacement has expanded to include patients at intermediate- and low-risk cohorts. We sought to determine disease prevalence and treatment distribution including transcatheter aortic valve replacement eligibility in low-risk patients across 37 advanced economies. Methods and Results— Four systematic searches were conducted across MEDLINE, EMBASE, and the Cochrane database for studies evaluating disease prevalence, severity, decision making, and survival in patients with aortic stenosis. Estimates of disease prevalence and treatment eligibility were calculated using stochastic simulation and population data for the 37 countries comprising the International Monetary Fund’s advanced economies index. Fifty-six studies comprising 42 965 patients were included across 5 domains: prevalence, severity, symptom status, treatment modality, and outcome. The pooled prevalence in the general population aged 60 to 74 years and >75 ...
Bio-inspired polymeric heart valves (PHVs) are excellent candidates to mimic the structural and t... more Bio-inspired polymeric heart valves (PHVs) are excellent candidates to mimic the structural and the fluid dynamic features of the native valve. PHVs can be implanted as prosthetic alternative to currently clinically used mechanical and biological valves or as potential candidate for a minimally invasive treatment, like the transcatheter aortic valve implantation. Nevertheless, PHVs are not currently used for clinical applications due to their lack of reliability. In order to investigate the main features of this new class of prostheses, pulsatile tests in an in-house pulse duplicator were carried out and reproduced in silico with both structural Finite-Element (FE) and Fluid-Structure interaction (FSI) analyses. Valve kinematics and geometric orifice area (GOA) were evaluated to compare the in vitro and the in silico tests. Numerical results showed better similarity with experiments for the FSI than for the FE simulations. The maximum difference between experimental and FSI GOA at m...
W ith this paper was inadvertently published an unaffiliated Supporting Information document; it ... more W ith this paper was inadvertently published an unaffiliated Supporting Information document; it has been replaced with the correct file.
Macroscopic capsules, with tunable properties based on hierarchical self-assembly on multiple len... more Macroscopic capsules, with tunable properties based on hierarchical self-assembly on multiple lengthscales, are prepared from the co-operative self-assembly of polysaccharide and peptide amphiphiles.
The bola-amphiphilic arginine-capped peptide RFL4RF self-assembles into nanotubes in aqueous solu... more The bola-amphiphilic arginine-capped peptide RFL4RF self-assembles into nanotubes in aqueous solution. The nanostructure and rheology are probed by in situ simultaneous rheology/small-angle scattering experiments including rheo-SAXS, rheo-SANS, and rheo-GISANS (SAXS: small-angle X-ray scattering, SANS: small-angle neutron scattering, GISANS: grazing incidence small-angle neutron scattering). Nematic alignment of peptide nanotubes under shear is observed at sufficiently high shear rates under steady shear in either Couette or cone-and-plate geometry. The extent of alignment increases with shear rate. A shear plateau is observed in a flow curve measured in the Couette geometry, indicating the presence of shear banding above the shear rate at which significant orientation is observed (0.1-1 s(-1)). The orientation under shear is transient and is lost as soon as shear is stopped. GISANS shows that alignment at the surface of a cone-and-plate cell develops at sufficiently high shear rate...
Journal of biomechanical engineering, Jan 28, 2016
Styrene based block co-polymers are promising materials for the development of a polymeric heart ... more Styrene based block co-polymers are promising materials for the development of a polymeric heart valve prosthesis (PHV); the mechanical properties of these polymers can be tuned via the manufacturing process, orienting the cylindrical domains to achieve material anisotropy. The aim of this work is the development of a computational tool for the optimisation of the material microstructure in a new PHV intended for aortic valve replacement to enhance the mechanical performance of the device. An iterative procedure was implemented to orient the cylinders along the maximum principal stress direction of the leaflet. A numerical model of the leaflet was developed; the polymer mechanical behaviour was described by a hyperelastic anisotropic constitutive law. A custom routine was implemented to align the cylinders with the maximum principal stress direction in the leaflet for each iteration. The study was focused on valve closure, since during this phase the fibrous structure of the leaflet...
Background/Introduction Aortic Stenosis (AS) is the most frequent valvular pathology in the devel... more Background/Introduction Aortic Stenosis (AS) is the most frequent valvular pathology in the developed world. Whilst much is known about its pathogenesis and treatment, a paucity of data exists on the prevalence and number of patients eligible for valve replacement.
The International journal of artificial organs, Jan 30, 2015
Only mechanical and biological heart valve prostheses are currently commercially available. The f... more Only mechanical and biological heart valve prostheses are currently commercially available. The former show longer durability but require anticoagulant therapy; the latter display better fluid dynamic behavior but do not have adequate durability. New Polymeric Heart Valves (PHVs) could potentially combine the hemodynamic properties of biological valves with the durability of mechanical valves. This work presents a hydrodynamic evaluation of 2 groups of newly developed supra-annular, trileaflet prosthetic heart valves made from styrenic block copolymers (SBC): Poli-Valves. 2 types of Poli-Valves made of SBC and differing in polystyrene fraction content were tested under continuous and pulsatile flow conditions as prescribed by ISO 5840 Standard. A pulse duplicator designed ad hoc allowed the valve prototypes to be tested at different flow rates and frequencies. Pressure and flow were recorded; pressure drops, effective orifice area (EOA), and regurgitant volume were computed to asses...
Load-bearing tissues are composite materials that depend strongly on anisotropic fibre arrangemen... more Load-bearing tissues are composite materials that depend strongly on anisotropic fibre arrangement to maximise performance. One such tissue is the heart valve, with orthogonally arranged fibrosa and ventricularis layers. Their function is to maintain mechanical stress while being resilient. It is postulated that while one layer bears the applied stress, the orthogonal layer helps to regenerate the microstructure when the load is released. The present paper describes changes in the microstructure of a block copolymer with cylindrical morphology, having a bio-inspired microstructure of anisotropic orthogonally oriented layers, under uniaxial strain. To allow structural observations during fast deformation, equivalent to the real heart valve operation, we used a synchrotron X-ray source and recorded 2D SAXS patterns in only 1 ms per frame. The deformation behaviour of the composite microstructure has been reported for two arrangements of the cylinders in skin and core layers. The behav...
The mechanical behavior of three styrenic thermoplastic block copolymer elastomers with applied s... more The mechanical behavior of three styrenic thermoplastic block copolymer elastomers with applied surgical sutures was studied by uniaxial tensile testing. The materials exhibited oriented cylindrical microstructure. Distinct macroscopic deformation mechanisms have been observed upon stretching of samples with vertical and horizontal orientation. Deformation progressed along the axis of the suture in samples with parallel orientation (P), while it in case of normal orientation (N) the whole sample responded to the applied force. Also the analysis of the stress-strain curves showed a significant difference between samples P and N. Greater stress at break was observed for samples P, while samples N showed the capability to tolerate higher strain. The influence of morphology on the tear-out shape has been also observed. The thread made a vertical tear out in samples P while for samples N ripping off the bottom was observed.
ASME 2010 Summer Bioengineering Conference, Parts A and B, 2010
ABSTRACT Severe stenotic or insufficient native heart valves (nHV) must be substituted with artif... more ABSTRACT Severe stenotic or insufficient native heart valves (nHV) must be substituted with artificial heart valve prostheses (aHV) to prevent heart failure. Nowadays, surgeons can implant two types of aHVs: mechanical aHV or bioprosthetic aHV. Mechanical aHVs, which are built up from synthetic hard materials, assure good reliability but require daily anticoagulant treatment to avoid blood cells damage. On the contrary, bioprosthetic aHVs, which are made from animal or human tissues, display better hemocompatibility but significant risk of failure due to tissue degradation. Despite current development in manufacturing of valve prostheses, long-term clinical applications claim for new generation of aHVs able to meet reliability and effectiveness requirements [2].
A bi-directional, layered microstructure in cylinder forming block copolymers results from the lo... more A bi-directional, layered microstructure in cylinder forming block copolymers results from the local balance of shear and extensional flow during slow injection moulding.
Soft Matter, 2011, Advance Article DOI:10.1039/C1SM06503C (Paper) PDF Version. A real time SAXS s... more Soft Matter, 2011, Advance Article DOI:10.1039/C1SM06503C (Paper) PDF Version. A real time SAXS study of oriented block copolymers during fast cyclical deformation, with potential application for prosthetic heart valves. Joanna ...
This research investigates the dynamics of mechanical and structural transformations of styrenebu... more This research investigates the dynamics of mechanical and structural transformations of styrenebutadiene-styrene block copolymer, known as RCM1, which has cylindrical mesophase morphology. The polymer was processed using a Multipass Rheometer (MPR) with simultaneous X-ray observation. The method allowed investigation of the dynamics with 1 second time resolution. Samples were processed at 160 C and an apparent wall shear rate in the range $1.4 to 1125 s À1. Microstructural alignment was quantified using a second order X-ray orientation function. The polymer showed self-organization in the melt, aligning along the capillary walls. Shear flow disrupted the organization, which then rebuilt during the post-shearing pause, as the residual pressure relaxed across the capillary. The dynamics of structure ordering and disordering was a function of shear rate. The transition was faster for high shear rate cycles.
A degradation study of polystyreneepolybutadieneepolystyrene and polyisopreneepolystyrenee polyis... more A degradation study of polystyreneepolybutadieneepolystyrene and polyisopreneepolystyrenee polyisoprene in both dichloromethane and hexane solvents is presented. Alternative solvents for metathetic degradation provide the potential for greener chemistry, better selectivity, and control over the products. The catalyst concentration and solvent selection both determine the products formed. The degradation of polyisoprene and polybutadiene in a particular solvent was controlled by the solubility of polyisoprene/polybutadiene, and by its solubility relative to polystyrene. A large difference in solubility between the polymers in the selected solvent provides an additional driving force for block separation, encouraging reaction close to the interface between different blocks. Furthermore, solubility of the block copolymer speeds the degradation reaction. This tailoring of the reaction mechanism yields a new control over the products of polymer degradation.
The 2nd International Conference on Biomedical Engineering and Biotechnology (iCBEB 2013), held i... more The 2nd International Conference on Biomedical Engineering and Biotechnology (iCBEB 2013), held in Wuhan on 11–13 October 2013, is an annual conference that aims at providing an opportunity for international and national researchers and practitioners to present the most recent advances and future challenges in the fields of Biomedical Information, Biomedical Engineering and Biotechnology. The papers published by this issue are selected from this conference, which witnesses the frontier in the field of Biomedical Engineering and Biotechnology, which particularly has helped improving the level of clinical diagnosis in medical work.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
h i g h l i g h t s • Three intercalation regions of the bentonite interlayers according to the s... more h i g h l i g h t s • Three intercalation regions of the bentonite interlayers according to the surfactant type. • Non-ionic surfactant inhibited intercalation and changed interlayer conformation. • Lecithin caused extensive bentonite intercalation and increased thermal stability.
A novel polymeric heart valve shows durability equivalent to 25 years in accelerated bench testin... more A novel polymeric heart valve shows durability equivalent to 25 years in accelerated bench testing, in vitro hydrodynamics equivalent to existing bioprosthetic valves; and good performance in a small acute feasibility study in sheep.
Circulation: Cardiovascular Quality and Outcomes, 2017
Background— In recent years, use of transcatheter aortic valve replacement has expanded to includ... more Background— In recent years, use of transcatheter aortic valve replacement has expanded to include patients at intermediate- and low-risk cohorts. We sought to determine disease prevalence and treatment distribution including transcatheter aortic valve replacement eligibility in low-risk patients across 37 advanced economies. Methods and Results— Four systematic searches were conducted across MEDLINE, EMBASE, and the Cochrane database for studies evaluating disease prevalence, severity, decision making, and survival in patients with aortic stenosis. Estimates of disease prevalence and treatment eligibility were calculated using stochastic simulation and population data for the 37 countries comprising the International Monetary Fund’s advanced economies index. Fifty-six studies comprising 42 965 patients were included across 5 domains: prevalence, severity, symptom status, treatment modality, and outcome. The pooled prevalence in the general population aged 60 to 74 years and >75 ...
Bio-inspired polymeric heart valves (PHVs) are excellent candidates to mimic the structural and t... more Bio-inspired polymeric heart valves (PHVs) are excellent candidates to mimic the structural and the fluid dynamic features of the native valve. PHVs can be implanted as prosthetic alternative to currently clinically used mechanical and biological valves or as potential candidate for a minimally invasive treatment, like the transcatheter aortic valve implantation. Nevertheless, PHVs are not currently used for clinical applications due to their lack of reliability. In order to investigate the main features of this new class of prostheses, pulsatile tests in an in-house pulse duplicator were carried out and reproduced in silico with both structural Finite-Element (FE) and Fluid-Structure interaction (FSI) analyses. Valve kinematics and geometric orifice area (GOA) were evaluated to compare the in vitro and the in silico tests. Numerical results showed better similarity with experiments for the FSI than for the FE simulations. The maximum difference between experimental and FSI GOA at m...
W ith this paper was inadvertently published an unaffiliated Supporting Information document; it ... more W ith this paper was inadvertently published an unaffiliated Supporting Information document; it has been replaced with the correct file.
Macroscopic capsules, with tunable properties based on hierarchical self-assembly on multiple len... more Macroscopic capsules, with tunable properties based on hierarchical self-assembly on multiple lengthscales, are prepared from the co-operative self-assembly of polysaccharide and peptide amphiphiles.
The bola-amphiphilic arginine-capped peptide RFL4RF self-assembles into nanotubes in aqueous solu... more The bola-amphiphilic arginine-capped peptide RFL4RF self-assembles into nanotubes in aqueous solution. The nanostructure and rheology are probed by in situ simultaneous rheology/small-angle scattering experiments including rheo-SAXS, rheo-SANS, and rheo-GISANS (SAXS: small-angle X-ray scattering, SANS: small-angle neutron scattering, GISANS: grazing incidence small-angle neutron scattering). Nematic alignment of peptide nanotubes under shear is observed at sufficiently high shear rates under steady shear in either Couette or cone-and-plate geometry. The extent of alignment increases with shear rate. A shear plateau is observed in a flow curve measured in the Couette geometry, indicating the presence of shear banding above the shear rate at which significant orientation is observed (0.1-1 s(-1)). The orientation under shear is transient and is lost as soon as shear is stopped. GISANS shows that alignment at the surface of a cone-and-plate cell develops at sufficiently high shear rate...
Journal of biomechanical engineering, Jan 28, 2016
Styrene based block co-polymers are promising materials for the development of a polymeric heart ... more Styrene based block co-polymers are promising materials for the development of a polymeric heart valve prosthesis (PHV); the mechanical properties of these polymers can be tuned via the manufacturing process, orienting the cylindrical domains to achieve material anisotropy. The aim of this work is the development of a computational tool for the optimisation of the material microstructure in a new PHV intended for aortic valve replacement to enhance the mechanical performance of the device. An iterative procedure was implemented to orient the cylinders along the maximum principal stress direction of the leaflet. A numerical model of the leaflet was developed; the polymer mechanical behaviour was described by a hyperelastic anisotropic constitutive law. A custom routine was implemented to align the cylinders with the maximum principal stress direction in the leaflet for each iteration. The study was focused on valve closure, since during this phase the fibrous structure of the leaflet...
Background/Introduction Aortic Stenosis (AS) is the most frequent valvular pathology in the devel... more Background/Introduction Aortic Stenosis (AS) is the most frequent valvular pathology in the developed world. Whilst much is known about its pathogenesis and treatment, a paucity of data exists on the prevalence and number of patients eligible for valve replacement.
The International journal of artificial organs, Jan 30, 2015
Only mechanical and biological heart valve prostheses are currently commercially available. The f... more Only mechanical and biological heart valve prostheses are currently commercially available. The former show longer durability but require anticoagulant therapy; the latter display better fluid dynamic behavior but do not have adequate durability. New Polymeric Heart Valves (PHVs) could potentially combine the hemodynamic properties of biological valves with the durability of mechanical valves. This work presents a hydrodynamic evaluation of 2 groups of newly developed supra-annular, trileaflet prosthetic heart valves made from styrenic block copolymers (SBC): Poli-Valves. 2 types of Poli-Valves made of SBC and differing in polystyrene fraction content were tested under continuous and pulsatile flow conditions as prescribed by ISO 5840 Standard. A pulse duplicator designed ad hoc allowed the valve prototypes to be tested at different flow rates and frequencies. Pressure and flow were recorded; pressure drops, effective orifice area (EOA), and regurgitant volume were computed to asses...
Load-bearing tissues are composite materials that depend strongly on anisotropic fibre arrangemen... more Load-bearing tissues are composite materials that depend strongly on anisotropic fibre arrangement to maximise performance. One such tissue is the heart valve, with orthogonally arranged fibrosa and ventricularis layers. Their function is to maintain mechanical stress while being resilient. It is postulated that while one layer bears the applied stress, the orthogonal layer helps to regenerate the microstructure when the load is released. The present paper describes changes in the microstructure of a block copolymer with cylindrical morphology, having a bio-inspired microstructure of anisotropic orthogonally oriented layers, under uniaxial strain. To allow structural observations during fast deformation, equivalent to the real heart valve operation, we used a synchrotron X-ray source and recorded 2D SAXS patterns in only 1 ms per frame. The deformation behaviour of the composite microstructure has been reported for two arrangements of the cylinders in skin and core layers. The behav...
The mechanical behavior of three styrenic thermoplastic block copolymer elastomers with applied s... more The mechanical behavior of three styrenic thermoplastic block copolymer elastomers with applied surgical sutures was studied by uniaxial tensile testing. The materials exhibited oriented cylindrical microstructure. Distinct macroscopic deformation mechanisms have been observed upon stretching of samples with vertical and horizontal orientation. Deformation progressed along the axis of the suture in samples with parallel orientation (P), while it in case of normal orientation (N) the whole sample responded to the applied force. Also the analysis of the stress-strain curves showed a significant difference between samples P and N. Greater stress at break was observed for samples P, while samples N showed the capability to tolerate higher strain. The influence of morphology on the tear-out shape has been also observed. The thread made a vertical tear out in samples P while for samples N ripping off the bottom was observed.
ASME 2010 Summer Bioengineering Conference, Parts A and B, 2010
ABSTRACT Severe stenotic or insufficient native heart valves (nHV) must be substituted with artif... more ABSTRACT Severe stenotic or insufficient native heart valves (nHV) must be substituted with artificial heart valve prostheses (aHV) to prevent heart failure. Nowadays, surgeons can implant two types of aHVs: mechanical aHV or bioprosthetic aHV. Mechanical aHVs, which are built up from synthetic hard materials, assure good reliability but require daily anticoagulant treatment to avoid blood cells damage. On the contrary, bioprosthetic aHVs, which are made from animal or human tissues, display better hemocompatibility but significant risk of failure due to tissue degradation. Despite current development in manufacturing of valve prostheses, long-term clinical applications claim for new generation of aHVs able to meet reliability and effectiveness requirements [2].
A bi-directional, layered microstructure in cylinder forming block copolymers results from the lo... more A bi-directional, layered microstructure in cylinder forming block copolymers results from the local balance of shear and extensional flow during slow injection moulding.
Soft Matter, 2011, Advance Article DOI:10.1039/C1SM06503C (Paper) PDF Version. A real time SAXS s... more Soft Matter, 2011, Advance Article DOI:10.1039/C1SM06503C (Paper) PDF Version. A real time SAXS study of oriented block copolymers during fast cyclical deformation, with potential application for prosthetic heart valves. Joanna ...
This research investigates the dynamics of mechanical and structural transformations of styrenebu... more This research investigates the dynamics of mechanical and structural transformations of styrenebutadiene-styrene block copolymer, known as RCM1, which has cylindrical mesophase morphology. The polymer was processed using a Multipass Rheometer (MPR) with simultaneous X-ray observation. The method allowed investigation of the dynamics with 1 second time resolution. Samples were processed at 160 C and an apparent wall shear rate in the range $1.4 to 1125 s À1. Microstructural alignment was quantified using a second order X-ray orientation function. The polymer showed self-organization in the melt, aligning along the capillary walls. Shear flow disrupted the organization, which then rebuilt during the post-shearing pause, as the residual pressure relaxed across the capillary. The dynamics of structure ordering and disordering was a function of shear rate. The transition was faster for high shear rate cycles.
A degradation study of polystyreneepolybutadieneepolystyrene and polyisopreneepolystyrenee polyis... more A degradation study of polystyreneepolybutadieneepolystyrene and polyisopreneepolystyrenee polyisoprene in both dichloromethane and hexane solvents is presented. Alternative solvents for metathetic degradation provide the potential for greener chemistry, better selectivity, and control over the products. The catalyst concentration and solvent selection both determine the products formed. The degradation of polyisoprene and polybutadiene in a particular solvent was controlled by the solubility of polyisoprene/polybutadiene, and by its solubility relative to polystyrene. A large difference in solubility between the polymers in the selected solvent provides an additional driving force for block separation, encouraging reaction close to the interface between different blocks. Furthermore, solubility of the block copolymer speeds the degradation reaction. This tailoring of the reaction mechanism yields a new control over the products of polymer degradation.
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Papers by Joanna Stasiak